Additive manufacturing (also known as “3D printing”) is performed by a special-purpose device which operates by depositing thin layers of thermoplastic or other reformable or reactive material onto a flat planar surface. This is done by depositing said material between precise points until the sum of all layers forms the ultimate shape of a desired object. One requirement that this type of system has is that the first layer of material deposited on the build surface must adhere to that surface. This adhesion is important because it ensures that the forces of the subsequent material being deposited does not change the position of the first layer relative to all subsequent layers. While a lateral shift of any layer results in inaccurate printing, a shift in the first layer typically results in catastrophic failure of the print job.
This adhesion requirement introduces a certain “Goldilocks” paradigm: a print surface must provide sufficient adhesion such that the risk of first layer detachment over the course of a print job is sufficiently low, yet not so much adhesion that the desired object is now permanently fused to the build platform. Put simply, a build platform that provides too much adhesion requires significant physical force to remove the object, while a build platform with too little adhesion causes the printer to be unreliable or inaccurate.
Already existing in the art are a number of solutions to address this adhesion requirement, however each solution has significant limitations or drawbacks. Such solutions include painter's tape, ultra-hold hair spray, and polyimide tape. Each of these materials are produced by a variety of companies, each with their own specific chemical formulations. However, a common drawback of all these materials is that they lack staying power. That is, they all wear out or become damaged during the removal of the print, possibly after only a single use.
Another solution to the adhesion requirement of 3D printing is to have the build platform be inherently adhesive. To address ejecting the printed objects, some of these build platforms are constructed out of a flexible base material, which allows the end user to apply a bending force to the build platform to unstick the printed object from the build platform.
Regardless of the composition of the build platform, most 3D printers that exist today merely leave the completed object on the build platform, waiting for the user to manually remove the object so that the next print job can initialize. This creates a bottleneck in the production of 3D-printed objects, preventing 3D printing from being used as a manufacturing tool. Because of this, 3D printers cannot automatically process their print queues, and cannot be operated with any kind of autonomy. For 3D printers to fulfill the vision as deliverers of digital ideas into our physical world, a mechanism for removing a print job from the build platform is necessary.
One solution to this automated ejection problem is the “Automated Build Platform” product offered as an aftermarket add-on kit by MakerBot Industries, disclosed in U.S. Pat. Nos. 8,282,380 and 8,287,794. There, the build platform surface is constructed out of a thin, flexible substance concatenated with itself to form a closed-loop, movable conveyor belt, supported by an underlying flat hard surface. Once printing is completed, the conveyor belt advances using the rotational force of motorized frictional cylinders on one end, and the object detaches from the flexible surface at the rotating point, also pushing it from the completed build platform. The movement of the build surface as a conveyor belt both provides the detaching force at the rotation point as well as the linear movement of the object out of the build space. However, when implemented in real-world printers, warping of the object proved to be an insurmountable problem as a print bed that ejects warped objects is not functional. That is, the upward curling force of uneven thermoplastic cooling was too great for the thin surface material to counteract, and objects with large surface areas were either too warped to be acceptable, warped to the point of causing catastrophic print failure, or in the event of a small object not being large enough to warp, too well-adhered to be removed by the rotating force of the surface. Attempts were made to correct this by constructing the build platform out of thin metal, like titanium. Notwithstanding the dramatically increased cost of a titanium build platform, large objects still produced the devastating warping effects that the thin metal couldn't counteract.
Another solution that exists today is taught in U.S. Pat. No. 9,289,946. That solution leverages the mechanical advantage of a wedge and uses a blade to apply a separating force to break the bonds between the bottom surface of the printed object and the printing surface. Further, the blade's motion-path back to its starting position doubles as the force to push the now-separated object out from the build volume. Alternatively, this blade/wedge-separation method may employ a secondary, separate device to remove the object from the print area after separation to similar effectiveness at the cost of increased expenses and mechanical complexity, should there be an engineering reason to do so. However, this solution is mechanically complex and has limits on the size of objects that can be ejected because as an object's bottom surface area increases, the force of adhesion between the object and the build platform increases as well. Therefore, the force needed to drive a blade underneath the first layer of the build object increases drastically with the footprint of the build object. Additionally, the blade may dull over time, requiring sharpening or replacement, adding to a printer's maintenance overhead. The blade also requires exact calibration, as the blade must run along the surface of the build platform, but not cause damage or excessive wear to it. Finally, this mechanism requires additional space alongside an arbitrary axis of the build surface area, decreasing the printer-size-to-build-volume ratio of the 3D printer.
The most prolific automated solution to ejecting printed objects from the build platform is the automated application of a large brute force on the completed object. This force is sufficient such that the bottom layer of the printed object detaches from the build platform and the object's momentum moves it out from the printer's build volume, freeing the printer to initialize a subsequent print. This is achieved via a dedicated ramming device or via the print head itself. The success of this method is firstly dependent on the condition that the force on the object is sufficient such that separation occurs between the object and the build platform, as there is no mechanical advantage to this method. In the case of using the print head to ram the object off the build platform, the components that support the print head must be able to withstand this force. Typically, the supports are precision-machined guide rods, which, for small objects, are sufficient. However, for large objects with a high degree of adhesion to the build surface, the force of impact may be sufficient to permanently deform the rods that allow the motion of the print head, effectively breaking the printer until they are replaced. This method also requires that the adhesion between layers of the object is higher than the adhesion between the object and the build surface, otherwise the object would shear at an arbitrary z-height, which could cause either errors or breakage of the printer when attempting to print the next object. With this method being effective only for printed objects that are strong in their inherent shape and small in their surface area contact with the print platform, this method leaves much to be desired.
Another solution is taught by International Patent Application No.: WO 2015/116639. This invention consists of two critical components: a flexible, flat planar build surface; and a two-part mechanical system to deform this surface along one axis and then also to vacate the now-freed completed object from the build surface. The combination of deformable planar surface and mechanical system serve to replace the need for human labor to clear a printer's build surface for a subsequent print to commence. This method is dependent on the aforementioned “goldilocks” build platforms which are constructed out of a flexible metal surface coated with a substance that increases desirable adhesion properties between printed plastic and the build platform, or a flexible non-metal material that inherently has desirable adhesion properties. Between the coated-metal vs. proprietary inherent material flexible products, flatness of the build surface is difficult to achieve or is highly expensive. Additionally, the natural fatigue of both metal and polymer flexible build products must be considered. After certain flex/flatten cycles, the material may either begin to crack or degrade from the stress, or possibly no longer be able to return to a fully flattened state—a hard-stop for accurate 3D printing, again leaving much room for improvement.
As can be seen based on the above solution, the current state of the art only provides very compromised options, either limiting the type of object that can be printed or adding significant mechanical complexity and chemical-manufacturing dependencies to the 3D printer itself.
While these units may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present disclosure as disclosed hereafter.
In the present disclosure, where a document, act, or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act, item of knowledge, or any combination thereof that was known at the priority date, publicly available, known to the public, part of common general knowledge or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which the present disclosure is concerned.
While certain aspects of conventional technologies have been discussed to facilitate the present disclosure, no technical aspects are disclaimed. It is contemplated that the claims may encompass one or more of the conventional technical aspects discussed herein.